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Deflection Yoke

deflection yoke

To make a beam of electrons do something useful, it has to be deflected from its course in some manner so as to make a trace or scan across the CRT’s faceplate. There are two methods used to do this: with an electrostatic charge and an electro-magnetic field. Electrostatic deflection uses pairs of charged plates … Read more

Deflection Circuit

beam length

The deflection yoke’s electromagnets are used to alter the path of the electron beam in a CRT. The job of synchronising the influence exerted by each of the yoke’s two magnets, and so controlling the directing of the beam towards specific parts of the screen, is handled by some electronics known as the deflection circuit. … Read more

Control Grid

control grid

Although the Braun tube contained all the essential elements of the modern CRT, these existed in a fairly primitive form and it lacked many of the refinements which are now considered as basic components. In the years following Braun’s work, one of his assistants, Jonathan Zenneck, added a second aperture to the neck of Braun’s … Read more

Braun Tube

braun tube

The development of the first CRT was the culmination of many years, or in this case, centuries, of research and discovery which put into place all the necessary elements. These include: the first manmade phosphor (1603); the first gas discharge tube (1751); the first production of light by exciting a phosphor with an electrical discharge … Read more

Bi/Tri-Linear Filtering

without bi

A simple form of texture filtering, point sampling, could be used to scale textures prior to their being mapped onto surfaces in a 3D scene. This technique could easily introduce errors by taking a too simple approach to the task. Using a more sophisticated, though slower, technique called “bi-linear filtering”, the colour of each pixel … Read more

Beam-Focusing

beam focusing

There are parts of the CRT that control the production, flow, acceleration and direction of the tube’s electron beam but leave its shape unaltered.  As the electrons accelerate towards the screen, they tend to diverge, as they all have a similar negative charge. If this divergence were to continue, the beam’s diameter when it reached … Read more

Aperture Grille

aperture grille

Before the three-gun, shadow mask CRT was firmly established as a standard for producing colour CRTs, several other novel systems were developed. One of these was the PDF (Post Deflection Focusing) Chromatron developed at the University of California. This tube had a single electron gun addressing a pattern of continuous vertical phosphor stripes on its … Read more

Antialiasing

antialiasing

Antialiasing, as the name suggests, is a technique used to combat an effect known as aliasing. When a line is drawn on a piece of paper, its edges appear smooth regardless of the line’s orientation. When a line is drawn on a computer display, whether CRT- or LCD-based, the limited resolution of the display means … Read more

Anode

anode

The control grid regulates the number of electrons which are allowed to leave the gun of a CRT by using a negative voltage to repel the electrons. Once free of the control grid’s influence, the electrons then need to be accelerated down the tube to ensure that they strike the phosphor face-plate lining with sufficient … Read more

Anistropic Filtering

Anisotropic means “non-uniform shape” and it is because this filtering technique works on non-uniform, or uneven, shaped areas that it is more powerful, and takes much more processing power, than Point Sampling, bi-linear or tri-linear filtering. One of the problems with these methods is that they rely on a square as their sampling area and … Read more

Alpha-Blending

alphablending

Alpha-blending is a technique which can be used when computer graphics are laid on top of each other and one or more of the objects contain a transparent, or semi-transparent, portion. It ensures that the pixels of the graphic which are underneath a transparent area are visible through it and that their colour or brightness … Read more